An operational amplifier is a basic element in an analog circuit system and a hybrid signal system, and is generally used for an operation, driving, and the like. Currently, an output of the operational amplifier has non-ideal features, including a noise, a distortion, an offset, and the like. Consequently, quality of an output signal is severely affected, thereby affecting system performance. Particularly, when a system needs to output high power or drive a heavy load, that is, when the system needs to output with relatively high power or relatively high amplitude, specifically, for example, when the system is applied to an environment such as a headphone, an earphone, and a line driver, the non-ideal features such as the distortion and the noise of the output of the operational amplifier are obviously worse, and performance of the operational amplifier is severely affected.
A common operational amplification circuit used for driving a load usually uses a structure in which multiple stages of operational amplifiers are cascaded. In this cascading structure, non-ideal features of a signal increase stage by stage, and are accumulated at an output stage. When the operational amplification circuit drives a heavy load (that is, when an equivalent impedance of the load is low, and power output by the operational amplification circuit is high), the non-ideal features of the operational amplification circuit are severer. Therefore, a circuit system having a structure that can suppress the non-ideal features of the operational amplifier urgently needs to be designed.